Preparation of cyclo-trimethylenetrinitramine



Piatented Aug. 15, 1944 PREPARATION or CYCLO-TRHVIETHYLENE- TRINITRAMINE Joseph. A., Wyl er, Allentown, Pa., assignor to Trojan Powder Company, Allentown, Pa.

No Drawing.

Application January 12, 1943, Serial No. 472,167 7 8 Claims. (01. 260-248) This invention relates to the nitration of hexamethylenetetramine to cyclo-trim'ethylenetrinitramine commonly called Hexogen or Cyclonite.

It is well known that hexamethylenetetramine can be nitrated to cyclo-trimethylenetrinitramine by means of concentrated nitric acid, particularly an acid of a strength greater than 92% HNOs. However, in all known processes, the yields are usually lowvarying from 62% to 72% of theory.

It is also well known that the process of nitration which introduces either a nitrate group or a nitro group into an organic compound is usually improved by the presence of dehydrating agents in the nitrating bath. This improvement is generally in the yield of the nitrated product. Agents-which are known to increase such yields are sulfuric acid, P205, etc. 1 In the nitration Hexogen, we are concerned with the formation of anitramine, that is, the introduction of an N02 group into an amine'to form a nitrogen to nitrogen andnot a nitrogen to carbon bond. Also, we are concerned with the removal of a methylene amine substituent within the ring structure of the hexamethylenetetramine. Thus, hexamethylenetetramine: r

CH: N/ "Hz (5H: H:

a N upon nitration forms' -O2N'N/ N-Nofl H: Hi I with the methylene-amine substituent:

being set free and altered. v a

of hexamethylenetetramine to oleum, S03, phosphoric acid,

uent are not thoroughly known. It is known I! that most of the -CH2-- groups form CHzO and the evidence indicates the formation of only a small amount of NH3 under ideal nitrating conditions.

The presence of the CH2O in the nitrating bath is, however, a very important factor due to the ease of oxidation of CH2O by nitric acid, particularly by mixtures of nitric acid and dehydrating agents, and this oxidation has'a very deleterious effect upon the yield of Hexogen obtained in the nitration.

Now, I have found that in the nitration ofhexamethylenetetramine using nitric acid in combination with such powerful dehydration agents as mentioned above results are obtained which are no longer what would be expected on the basis of known facts regarding the use of these agents in well known 'nitrations. Thus, the additon of sulfuric acid or sulfuric acid and S0: to a HNO3 used for the nitration of hexamethylenetetramine does not improve the yield of nitration but actually lowers it; whereas, phosphoric acid, hydrated P205, or phosphoric acid and P205, or P205, do increase the yield of nitration when used under certain restricted conditions which will be indicated below. V

The principal object of my invention is to nitrate hexamethylenetetramine to Hexogen with a greater yield. Other objects will become apparent upon a further perusal of this specification.

In order more clearly to point out my invention, the following examples, in which all parts are by weight, are given.

Example #1 8 parts of hexamethylenetetramine were added, over a period of 12 minutes, with stirring, to 100 parts of 99% nitric acid, to which 5 parts of 104.62% H2SO4 had been added, keeping the temperature of the nitrating bath at 3 to 10 C. throughout the nitration. The mixture was stirred at about 5 C. for 15 minutes after all the hexamethylenetetramine had been added, when it was drowned in a large excess of cold water and the precipitated cyclo-trimethylenetrinitramine filtered ofi, washed with cold water, then with hot water, with alcohol and finally dried at C. to constant weight. The yield of cyclotrimethylenetrinitramine obtained was 9 parts or 71% of theory. Using the same, nitric acid, without the addition of anysulfuric acid, the yield was 72% of theory indicating that the addition of this small an amount of 104.62% oleum did not improve the yield of Hexogen obtained.

Example #4 Repeating Example #1, but using 20- parts of 104.62% sulfuric acid instead of 5 parts, gave a yield of Hexogen of 8 parts, or 63%v of theory.

These examples are given to show that the 104.62% sulfuric acid instead of 5 parts, gave a yield of Hexogen of 8 parts or only 63% of theory.

from 12 parts of hexamethy lenetetramine or 90% of theory.

Example #11 Repeating experiment #10, with the additional steps of adding 4 additional parts of P20 and 4 additional parts of hexamethylenetetramine the yield ofs'Hexogen obtained was19' parts from 16 parts of hexamethylenetetramine or 75% of theory. It should be noted that in this experiment 16 parts of hexamethylenetetramine and 25 parts of P205 were used for 100 parts of 99% presence of sulfuric acid or sulfuric acid and $03 in the nitric acid does not improve its nitrating qualities, when used on hexamethylenetetramine, but actually lowers it, particularly as the concentrationof H2804 is increased.

9 4 9 Example #5 P205'had been added. The temperature of the nitrating bath was held at to 0. throughout the nitration. The mixture was stirred at about 5 C. for minutes after all the hexamethylenetetramine had, been added, when it was drowned i'n'alarge excess of cold water and the thus precipitated cyclo*trimethylenetrinitramine' filtered off, washed with cold water, then with hot water, then with alcohol and finally dried at 60 C. to constant weight. The yield of Hexogen obtained was 9 parts or 81% of theory.

. Example #6 Example #5 was repeated,- using 6 parts of P205 insteadof 3 parts. The yield obtained was 10-parts or 90% of theory.

' Example #7 Example #5 was repeated, using 10 parts of P205 instead-of 3 parts. The yield obtained was 10 parts, or 90% of theory.

, Example#8 Using parts of P205 and 8 parts of hexamethylenetetramineand proceeding 'asabove gave'a yield of 11 parts, or 87% of theory.

Example #9 Repeating Example #8, but using 10 parts of Hexamethylenetetramine gave a yield of 82% of theory.

g Example #10 I 4 parts,of.hexamethylenetetramine were added, over a period of 10 minutes, with stirring,.to 100 parts of 99% nitric. acid, to which 10 parts of P205-had been added. After the addition of the My work has shownthat the use of more than about 25 parts of P205 for each 100 parts of nitric acid, calculated to 100% strength, is no longer effective in improving the yield of I-Iexogen in thenitration. Consequently, my invention is limited to the use of not more than about 25 parts of P205 to 100 parts of nitric acid (100%) Also, my bestresults are obtained by regulating the.P205 or water content of the nitrating acid to within certain limits during th nitration, that is,'my best results are obtained when the nitratingv acid is close to anhydrous HNOs throughout the nitration. It should be noted that although my best yields are obtained under anhydrous conditions I also obtain important improvements in yield with nitric acids of lower strengths, that is, as 7 low as about -90% HNO3. Consequently, my process is applicable to the use of nitric acid of a strength greater than about 85-90% HNOa treated with any amount of P205 not greater thanabout 25 parts of P205 per 100 parts of nitric acid 100%).

In this specification the term concentrated nitricacidi is used to cover any strength greater than about 85 to HNOa.

My work has shown that a nitrating acid comprising HNOs and H5P04; or HNOs, H3PO4 and P205; or I-INOs and P205 in such proportions that the free water content of the nitrating acid is not greater than about 4% and the negative water content not greater than about 4%, is the most practicable nitrating acid from the standpoint of yield of Hexogen from a given amount of hexamethylenetetramine.

The term negative water content, as appearing in the specification and the claims, is used to designate the analytical result obtained on a given nitrating acid by adding the nitric acid, the total phosphate calculated to H3P04 and the N02 in the acid and taking the difierence between this sum and as the water content; if the sum is greater than 100%, it shows that negative water is present and the difference between this sumrand 100% gives the negative Water.

I wish to emphasize that the examples and theories given above are merely illustrative or explanatory in nature and are not intended to limit my invention in any way not indicated by the appended claims. Thus I may use any temperature below about 30 0, although I prefer a range of from about 5 C. to 20" 0.; I may use any ratio of hexamethylenetetramine to I-INOa up to about 16 parts of hexamethylenetetramine to 100 parts of 100% HN03;,I may add the hexamethylenetetramine and the P205 simultaneously or successively; I may vary the rates of addition of reactants and times of stirring over a wide range or I may alter the method of recovery of the Cyclonite from the'nitrating bath without departing from the essence of my invention. Also,in all my examples, I have mentioned P205 as the dehydrating agent added, but since P205 in contact with water forms HP04 and other hydrates it is understood that I may at times use H3P'o4, or P205 in other states of hydration instead of P205 itself. Consequently, my use of the term P205 in the description may at times cover the P205 equivalent of the hydrated P205 present in the nitrating bath and is not intended to convey the though that the P205 necessarily exists in the solution as anhydrous P205. It is understood that P205 cannot exist in the anhydrous condition in contact with water.

I claim:

1. The process for the nitration of hexamethylenetetramine to cyclo-trimethy1enetrinitramine which comprises reacting hexamethylenetetramine, at a nitrating temperature, with concentrated nitric acid containing a phosphorus pentoxide, said phosphorus pentoxide being present in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by weight of nitric acid (100%), and said hexamethylenetetramine being added in an amount not in excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by Weight, of 100% HNOs; adding the reaction mixture to an excess of cold water, with stirring, and filtering ofi the cyclotrimethylenetrinitramine which precipitates.

2. The process for the nitration of hexamethylenetetramine to cyclo-trimethy1enetrinitramine which comprises reacting hexamethylenetetramine, at a nitrating temperature, with concentrated nitric acid containing a hydrated phosphorus pentoxide, said hydrated phosphorus pentoxide being present in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by weight, of nitric acid (100%) and said hexamethylenetetramine being added in an amount not in excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by weight, of 100% I-lNOg; adding the reaction mixture to an excess of cold water, with stirring, and filtering ofi" the cyclo-trimethy1enetrinitramine which precipitates.

3. The process for the nitration of hexamethylenetetramine to cyclo-trimethy1enetrinitramine which comprises reacting hexamethylenetetramine, at a nitrating temperature, with concentrated nitric acid containing P205, said P205 being present in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by weight, of nitric acid (100%), and said hexamethylenetetramine being added in an amount not in excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by weight, of 100% HNOs; adding the reaction mixture to an excess of cold water, with stirring, and filtering off the cyclo-trimethylenetrinitramine which precipitates.

4. The process for the nitration of hexamethylenetetramine to cyclotrimethylenetrinitramine which comprises adding hexamethylenetetramine, with stirring, at a temperature below 30 0., to a concentrated nitric acid containing a phosphorus pentoxide; said hexamethylenetetramine being added in an amount not in'excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by weight, of 100% I-INOs; said phosphorus pentoxide being present in an amount not in excess of 25 parts, by weight, of P205 per parts, by weight, of nitric acid (100%); adding the nitration mixture, with stirring, to an excess of cold water and filtering off the cyclotrimethylenetrim'tramine which precipitates.

5. The process for the nitration of hexamethylenetetramine to cyclo-trimethy1enetrinitramine which comprises adding hexamethylenetetramine, with stirring, at a temperature below 30 0., to a concentrated nitric acid containing a hydrated phosphorus pentoxide; said hexamethylenetetramine being added in an amount not in excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by weight, of 100% HNOa; said hydrated phosphorus pentoxide being present in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by Weight, of nitric acid (100%) adding the nitration mixture, with stirring, to an excess of cold water and filtering oil the cyclo-trimethylenetrinitramine which precipitates.

6. The process for the nitration of hexamethylenetetramine to cyclo-trimethy1enetrinitramine which comprises adding hexamethylenetetramine, with stirring, at a temperature below 30 0., to a concentrated nitric acid containing P205; said hexamethylenetetramine being added in an amount not in excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by weight, of 100% HNO3; said P205 being present in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by weight, of nitric acid (100%) adding the nitration mixture, with stirring, to an excess of cold water and filtering off the cyclo-trimethy1enetrinitramine which precipitates.

7. The process for the nitration of hexamethylenetetramine to cyclo-trimethy1enetrinitramine which comprises adding hexamethylenetetramine, with stirring, at a temperature below 30 0., to a concentrated nitric acid containing phosphoric acid; said hexamethylenetetramine being added in an amount not in excess of 16 parts, by weight, of hexamethylenetetramine per 100 parts, by weight, of 100% I-INOs; said phosphoric acid being present in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by weight, of nitric acid (100%); adding the nitration mixture, with stirring, to an excess of cold water and filtering off the cyclo-trimethylenetrinitramine which, precipitates.

8. The process for the nitration of hexamethylenetetramine to cyclo-trimethylenetrinitramine which comprises adding hexamethylenetetramine,

with stirring, at a temperature below 30 0., to a nitric acid containing between 4% of free water and 4% of negative water; said water-range being produced by the addition of P205 to the nitric acid; and said P205 being added in an amount not in excess of 25 parts, by weight, of P205 per 100 parts, by Weight, of HNOs (100%); adding the reaction mixture, with stirring, to an excess of cold water, filtering oil. the cyclo-trimethylenetrinitramine which precipitates, washing with water and drying.

JOSEPH A. WYLER. 

